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Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency
Published on: June 16, 2011
Coronaviruses: an RNA proofreading machine regulates replication fidelity and diversity
Mark R Denison1, Rachel L Graham, Eric F Donaldson
1Department of Pediatrics and Microbiology & Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
RNA Biology
|May 20, 2011
Summary
Coronaviruses (CoVs) possess a unique RNA proofreading machine, nsp14-ExoN, essential for maintaining genome integrity. Inactivating this exoribonuclease significantly increases mutation rates, revealing its critical role in viral evolution and pathogenesis.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- RNA viruses require a balance between adaptation and genome stability for survival.
- Coronaviruses (CoVs), within the order Nidovirales, possess the largest known RNA genomes (up to 32 kb).
- CoVs encode sixteen nonstructural proteins (nsp 1-16) involved in RNA synthesis and modification.
Purpose of the Study:
- To investigate the role of the 3'-to-5' exoribonuclease (ExoN) activity in nsp14 for coronavirus replication fidelity.
- To understand the implications of nsp14-ExoN for viral genome evolution and pathogenesis.
Main Methods:
- Genetic inactivation of nsp14-ExoN activity in SARS-CoV and murine hepatitis virus (MHV) using alanine substitution at conserved active site residues.
- Analysis of mutation rates in engineered viral mutants.
Main Results:
- Inactivation of nsp14-ExoN resulted in viable mutants with 15- to 20-fold increases in mutation rates.
- These mutation rate increases were significantly higher than those observed in fidelity mutants of other RNA viruses.
- nsp14-ExoN is essential for maintaining replication fidelity in CoVs.
Conclusions:
- nsp14-ExoN functions as a key component of an RNA proofreading machine, unprecedented in RNA virus biology.
- Understanding nsp14-mediated proofreading offers insights into RNA virus evolution, fidelity, diversity, and pathogenesis.
- Viral replication fidelity may be adaptable, rather than fixed, in response to environmental pressures.
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